1. Field of the Invention
The present invention relates to a sliding-vane rotary compressor for compressing a refrigeration medium, for example.
2. Description of the Prior Art
Sliding-vane rotary compressors, as disclosed for example in Japanese Utility Model Laid-Open Publication No. 61-92778, include a compressor body composed of a cylinder block having an inside guide surface, and front and rear side blocks disposed on opposite ends of the cylinder block, and a rotor rotatably disposed in the compressor body and carrying thereon a plurality of radially movable sliding vanes held in contact with the guide surface of the cylinder block. The vanes, rotor, cylinder block and front and rear side blocks jointly define therebetween a plurality of compression chambers in which a refrigeration medium is compressed.
The rotor is concentrically and fixedly mounted on a drive shaft. The drive shaft is rotatably supported on the front and rear side blocks via a pair of bearings, with a clearance between the respective side block and the rotor for smooth rotation of the rotor.
A front side end of the drive shaft is operatively connected with an electromagnetic clutch which includes a clutch plate coupled with the front side end of the drive shaft and a rotor being driven by a driving force from a suitable drive means such as an engine. When the electromagnetic clutch is energized, the clutch plate is attracted to the rotor, thereby transmitting the drive force to the drive shaft. With the rotation of the rotor, the vanes slide along the guide surface of the cylinder block to cause the compression chambers to be subsequently increased and decreased in volume with each revolution of the rotor, whereby the refrigeration medium drawn into the compression chambers is compressed and discharged from the compression chambers through discharge holes by forcibly opening respective valves associated with the discharge holes.
A problem associated with the conventional sliding-vane rotary compressor of the foregoing construction is that an unpleasant noise is produced while the compressor is operating. More particularly, in a sliding-vane rotary compressor having a total of five sliding vanes, the torque fluctuates ten times per one revolution of the rotor and the load fluctuates five times per one revolution of the rotor. Such fluctuation of torque and load produces a higher harmonic reasonance of the rotor which in turn brings about resonant vibration of other components leading to generation of an unpleasant noise.
The unpleasant noise is produced due to the presence of a clearance provided between the front side block and the rotor and also between the rotor and the rear side block for smooth rotation of the rotor. With the clearance thus provided, the rotor is allowed to oscillate in the axial direction when subjected to forces produced periodically when the torque and load of the rotor fluctuate.